The present invention relates to a motor driven type bell striking device to be employed in electric bells, the device incorporating a cam coupled with the rotating drive shaft of an electric motor. The cam serves to translate the rotary motion of the motor to an oscillating action which then impels a piston, the piston then impelling a striking member which is coupled with the base or frame of the bell by a spring.
In a conventional motor driven bell of this type (Sakaguchi, U.S. Pat. No. 4,183,018) as shown in FIGS. 7 and 8, an electric motor 1 is coupled with a cam 2 which then is coupled with a hammer supporting plate 3 which is pivotably mounted on frame 5. By this mechanism, the rotary motion of the motor 1 is converted into an oscillatory motion of hammer supporting plate 3 approximately perpendicular to the striking action of hammer head 6a. The aforementioned hammer supporting plate 3 is coupled with hammer 6 by two springs, leading spring 7 and following spring 8. A bushing 10 which surrounds the shaft 6b of hammer 6 intervenes between leading spring 7 and following spring 8 and between their connection with hammer supporting plate 3. Leading spring 7 extends distally along and surrounding hammer shaft 6b, attaching to hammer head 6a. Following spring 8 extends proximally along and surrounding hammer shaft 6b, attaching to the innermost end of hammer shaft 6b via a washer 9.
Thus the vibrating motion of hammer supporting plate 3, and accordingly bushing 10 is transmitted to hammer 6 by leading spring 7 and following spring 8, thereby causing hammer head 6a to strike gong 11 repeatedly, thus producing a ringing sound. The hammer 6 is stabilized both proximally by bushing 10 and distally through a circular opening 12 in frame 5, thereby limiting its motion to one dimension. But a device of this construction has the following shortcomings:
(a) As it oscillates, hammer 6 must pass through both bushing 10 and the opening 12 in frame 5. Thus friction, hence damping of the transmitted vibrational energy occurs. Sound output is thereby diminished, loss of energy and increased wear occurs. PA1 (b) The implementation of hammer supporting plate 3 requires increased moving parts, hence increased potential for wear, malfunction, and frictional energy loss.
In light of the above described shortcomings, the inventors of the present invention have striven to develop an improved bell striking mechanism.